Insect repellent composition and method



3,000,720 Patented May 21, 1963 3,090,720 INSECT REPELLENT CQIVIPGSITIONAND METHQD Eugene E. Kenaga, Midland, Mich, assignor to The Dow ChemicalCompany, Midland, Mich, a corporation of Delaware No Drawing. Filed Aug.5, 1960, Ser. No. 47,588 Claims. (61. 167-31) This invention isconcerned with insect repellents and is particularly directed to amethod of repelling insects and a repellent composition employingcertain ct-(alkylimino)-chloro-o-cresols.

In recent years, the development of potent synthetic organic toxicantshas served to alleviate, in many instances, the problems of man and hisdomestic animals with respect to insects. However, many situations stillexist in which it has not been found possible to control insectinfestation and attack and where effective insect repellents aredesirable to promote the comfort and health of bothman and animals Thus,repellents for biting and sucking pests of man such as mosquitos,chiggers, black flies and ticks have been discovered primarily by thework done by the personnel of the United States Department ofAgriculture and as a result of such discovery, these repellents areWidely used. However, many other problems of insect repellency andattractancy still remain unsolved. Pests of long standing such as thehouse fly and the cockroach, with attendant disease and filth, remain inclose cohabitation with man. The problem here is not only one of killbut also the prevention of any intimate association of insects with foodand waste products of man and domestic animals. As yet, no satisfactorylong-lasting residual repellent for insects attacking domestic animals,particularly various species of flies such as deer flies and houseflies, has been discovered.

It is an object of the present invention to provide a novel compositionand method for the repelling of insects. It is a further object toprovide such method and composition characterized by ease of applicationand long-lasting beneficial results. An additional object is to providea method and composition for the repelling of insects on animals. Otherobjects will become apparent from the following specification andclaims.

According to the present invention, it has been discovered that certaino-cresol compounds, namely, a- (alkylimino)-chloro-o-cresols representedby the structure CH=NR wherein R is a lower alkyl group containing from1 to 4 carbon atoms, inclusive, and n is from 1 to 2, are highlyeffective for repelling insects. Particularly efiective and, therefore,the preferred a-(alkylimino) -chloro-o-cresols area-(alky-limino)-4,6-dichloro-o-cresols. The repellent compounds aresolids or liquids soluble in many organic solvents. It is among theadvantages of the invention that the a-(alkylimino)-chloro-o-cresols arecharacterized by marked persistency of insect repellent activity and bycase of application to the sites to be protected.

In carrying out the invention, a composition comprising the activea-(alkylimino)-chloro-o-cresols may be applied in any suitable fashionto supply an insect repellent amount. Thus, the o-cresol compounds maybe employed as sprays, dusts, lotions or salves and in organic solvents,aqueous dispersions, inert solids or creams as carrier. In the preferredmethod for practicing the present invention, organic solvents are usedas carriers. When the carrier is an organic solvent, suitable solventsinclude acetone, kerosene, naphthas, benzene, toluene, xylene and otherliquid hydrocarbons. A preferred solvent is an isoparaflinic hydrocarbonhaving a boiling range of approximately 260 to 800 F. Alternatively, theo-cresol compounds may be dissolved in a suitable solvent such as loweraliphatic alcohol to prepare lotions or be incorporated into creams orsalves adapted to be rubbed on the skin. Further, the active repellingagent may be dispersed in water to prepare aqueous spray dispersionssuitable, for example, for application to cattle and horses. Spraycompositions are also useful for application to foliage, buildings andrecreational areas. For aqueous spray applications, a wetting ordispersing agent is employed in its preparation. Examples of suitablewetting agents include sulfonated alkylbenzenes, alkylated arylpolyether alcohols such as Triton X.100, alkali metal, alkylarylsulfonates such as sodium and potassium alkylbenzene sulfonates andpotassium alkyltoluene sulfonates, sulfates of long chain aliphaticalcohol such as sodium lauryl sulfates, water-soluble salts of organicbases containing a hydrocarbon chain of 8 to 24 carbon atoms such ashydrochloric, sulfonic, formic and acetic acid salts of primary,secondary and tertiary amines such as octyl amines, dodecyl amines,octadecyl amines and octadecenyl amines as well as non-ionic emulsifyingagents such as the condensation products of mercaptans withethylenedioxide, sorbitan monolaurate, sorbitan monolauratepolyoxyethylene derivatives such as Tween 20, etc. For application inhousehold, shed and barn areas, particularly for control of non-flyinginsects such as cockroaches, the active repellent may be applieddispersed in solid inert carrier materials such as talc, pyrophyllite,attapulgite and kieselguhr. In other applications as dust, particularlyfor use on plants, the active ingredient may be dispersed on finelyground sodium fluosilicate. In addition, the repellent may be combinedwith other conventional spray materials to form insecticidal emulsionsor dispersions.

The concentration of the a-(alkylimino)-chloro-ocresol in abovecomposition may vary from 0.001 percent by weight to 95 percent byweight of the composition, depending on 'wether the composition is atreating composition or a concentrate composition and whether it is inthe form of a solid or a liquid. In aqueous liquid spray treatingcompositions, concentrations of from 0.01 percent to 5 percent by weightof the m-(alkylimino)- chloro-o-cresol are considered preferable. Theconcentration of the u-(alkylimino)-chloro-o-cresol in organic solventsin treating compositions may be from 0.01 to 5 percent by weight.Concentrate liquid compositions generally contain from about 2.5 topercent by weight of the a-(alkylimino)-chloro-o-cresol. Lotions, creamsand the like preferably contain from about 5 to 75 percent or more byweight. Solid concentrate compositions may contain the o-cresol compoundin amounts as high as percent by weight of the active compound. Solidtreating compositions generally contain 0.004 percent to 10 percent byweight of the o-cresol compound.

In the practice of the present invention, a sufidciency of treatingcomposition is applied so as to deposit over an area to be protectedfrom insect infestation from about 1 to 5000 milligrams of thea-(alkylimino)-chloro-ocresol per square foot of surface. Preferredamounts are from about 10 to 500 milligrams per square foot. Suitableconventional methods may be employed in practice. Thus, equeoussolutions or dispersions may be applied by brushing, dipping or sprayingwith conventional equipment; solid compositions may be applied bydusting Example 1 Cylindrical cages were fitted with filter paper on oneend and wire screen on the other. Into each cage were placed abouttwenty-five one day old adult house flies.

In separate operations, one of 4,6-dichloro-a-rnethylimino-o-cresol,4,6-dichloro-a-ethylimino-o-cresol,4,6-dichloro-a-normal-propylimino-o-cresol, 4,6 dichloroaisopropylirnino-o-cresol, 4,6-dichloro a normal-butylimino-o-cresol,4,6 dichloro-a-secondary-butylirnino-ocresol and4-chloro-a-normal-butylimino-o-cresol in ace tone (about 10 percentweight by volume of solvent) were dispersed on the filter paper sides ofthe various cages in an amount sufficient to deposit one of theiminocresols at a rate of about 3000 mg./sq. ft. After about a 3-4 hourinterval, the cages were investigated to determine the number of houseflies resting on the filter paper. It was found in all cases thatsubstantially all the flies were repelled by the iminocresol on thefilter paper and were found on the side of the cage away from the filterpaper. In check operations wherein filter paper ends of the cages wereuntreated, the flies were found randomly distributed on all surfaces ofthe cage.

Example 2 In a similar separate operation, filter paper ends of cageswere treated with one of 4,6-dichloro-a-isopropylimino-o-cresol and 4,6dichloro-a-normal-butylimino-ocresol in acetone in an amount suflicientto deposit about 3000 milligrams of one of the c'resols per square foot.The cages were allowed to stand for 7 days and thereafter infested withabout twenty-five one day old adult flies and thereafter examined todetermine the distribution of the flies in the cage. It was found thatsubstantially all flies were repelled from the filter paper and foundaway from the filter paper end of the cage. In check operationsemploying untreated filter paper, the flies were found distributedthroughout the cage.

Example 3 In operations carried out in a similar manner, good repellencyof flies is obtained with 4-chloro-a-isopropyh imino-o-cresol,4-chloro-u-secondary-butylimino-o-cresol andS-chloro-a-isopropylimino-o-creso1.

Example 4 In operations carried out in a manner similar to thatdescribed in Example 1, about twenty-five American cockroach nymphsabout eight weeks old were placed in cylindrical cages. The filter paperends of the cages were treated in separate operations with4,6-dichloro-u-normaL propylimino-o-cresol,4,6-dichloro-a-normal-butyliminoo-cresol and4-chloro-a-methylimino-o-cresol in acetone (about 10 percent weight byvolume of solvent). After about a 3 to 4 hour interval the cages wereexamined to determine the number of American cockroaches resting on thefilter paper. Substantially no cockroach was found on the filter paperbut were found on the screen away from the filter paper. In checkoperations wherein the filter paper ends of the cages were untreated,the cockroaches were found randomly distributed throughout the cage.

Example 5 Yearling Black Angus steers were sprayed'over the entire bodysurface while the animals were held tightly in a retaining crib with 100milliliters of a 2.5 percent solution of4,6-dichloro-u-normal-butylimino-o-cresol in refined kerosene. Thisamount provided about 200 milligrams per square foot of body surface. Ascheck, a number of cattle were left untreated. Observations were made atvarying intervals and the results were as follows:

Untreated cattle were heavily infested (approximately with horn andstable flies and were constantly agitated by them. Deer and horse flieswere also present in the controls.

Example 6 A 5 percent acetone solution of 4,6-dichloro-a-normal-'butylimino-o-cresol was applied to one square foot area near the hip andshoulder areas of the flanks of horses, these being the areas on horsesmost frequented by biting flies. The untreated portions of the horseserved as checks. Immediately after application and 24 hours afterapplication the horses were'examined for infestation by flies. It wasfound that in the areas treated with 4,6- dichloro-a-normalbutylimino-o-cresol there were no flies whereas in the untreated areasthere were 20-30'stable flies, 6-7 green-eyed tabanids, 1 black horsefly and several deer flies at both intervals.

Example 7 Concentrate compositions are prepared as follows:

(A) 25 parts by weight of 4,6-dichloro-u-methyl-iminoo-cresol, 65 partsof xylene and 10 parts of an alkylated aryl polyether alcohol (TritonX-lOO) are mechanically mixed together to obtain an emulsifia-ble liquidcomposition.

(B) 90 parts by weight of 4-chloro-u-normahbutylimono-o-cresol and 10parts of an alkyl aryl sulfonate (Acto 700) are mechanically mixedtogether to obtain a water-dispersible mixture.

These compositions may be dispersed in water to produce aqueouscompositions having desirable wetting and penetrating properties. Theseaqueous compositions are then employed to treat cattle in an amountsufficient to distribute the o-cresol compound in effectiveconcentrations.

Example 8 150 milliliters of a spray composition containing 5.04 gramsof 4,6-dichloro-a-isopentylimino-o-cresol in isoparaflin oil havingarflash point of F. was applied to the skin surfaces of a horse. Thedosage is 300 milligrams per square foot of body surface. Five hoursafter administration, examination reveals that the horse issubstantially free of flies.

Example 9 A dust composition suitable for application in buildings, barnand shed areas is prepared by intimately blending and hammermillingtogether Parts byweight 4,6-dichloro-anorm al-butylimino -o-cresol 10A-ttapulgite clay 86 Nacconol NR (sodium alkyl aryl sulfonate) 2 Daxad(polymerized sodium salt of alkyl aryl and aryl alkyl sulfonic acids)pared by heating substantially equimolar proportions of achlorohydroxyaldehyde having the structure (IJH OHO

Ola

wherein R represents a lower alkyl group containing from 1 to 4 carbonatoms, inclusive, and n is an integer of from 1 to 2, inclusive, and inintimate admixture therewith, a dispersing agent, wherein in saidcomposition, the a-(alkylimino)-chloro-o-creso1 is present in an amountof from 0.001 percent to 95 percent by weight.

2. An insect repellent composition comprising a 4,6-dichloro-a-alkylimino-o-cres0l having the structure wherein R representsa lower alkyl group containing from 1 to 4 carbon atoms, inclusive, andin intimate admixture therewith, a dispersing agent, wherein in saidcomposition, the 4,6-dicholro-a-alkylimino-o-cresol is present in anamount of from 0.001 percent to percent by weight.

3. An insect repellent composition comprising4,6-dichloro-a-(normal-butylimino)-o-creso1 and in intimate admixturetherewith, a dispersing agent, wherein said composition, the4,6-dichloro-a-(normal-butylimino-ocresol is present in an amount offrom 0.001 percent to 95 percent by weight.

4. A method for repelling insects which comprises applying to thesurface to be protected an u-(a1ky1imino)- chloro-o-cresol having thestructure wherein R represents a lower alkyl group containing from 1 to4 carbon atoms, inclusive, and n is an integer of from 1 to 2,inclusive.

5. A method for repelling insects which comprises applying to thesurface to be protected a 4,6-diChl0IO-ocalkylimino-o-cresol having thestructure wherein R represents a lower alkyl group containing from 1 to4 carbon atoms, inclusive.

References Cited in the file of this patent Chemical Abstracts, vol. 52,l8293f, 1958. Smith et al.: Journal of Economic Entomology, June 1949,pages 439-444.

1. AN INSECT REPELLANT COMPOSITION COMPRISING ANA(ALKYLIMINO)-CHLORO-O-CRESOL HAVING THE STRUCTURE